1. Field of the Invention
The present invention relates to external defibrillators. In particular, the present invention relates to a method and device for minimizing delay between the cessation of cardiopulmonary resuscitation and the delivering of a defibrillating shock to a patient.
2. Description of Prior Art
Sudden cardiac death is the leading cause of death in the United States. Most sudden cardiac death is caused by ventricular fibrillation (xe2x80x9cVFxe2x80x9d), in which the heart""s muscle fibers contract without coordination, thereby interrupting normal blood flow to the body. The only known effective treatment for VF is electrical defibrillation, in which an electrical pulse is applied to a patient""s heart. The electrical shock clears the heart of the abnormal electrical activity (in a process called xe2x80x9cdefibrillationxe2x80x9d) by depolarizing a critical mass of myocardial cells to allow spontaneous organized myocardial depolarization to resume.
The electrical pulse must be delivered within a short time after onset of VF in order for the patient to have any reasonable chance of survival. To be effective, the defibrillation shock must be delivered to the patient within minutes of the onset of VF. Studies have shown that defibrillation shocks delivered within one minute after the onset of VF achieve up to a 100% survival rate. However, the survival rate falls to approximately 30% after only 6 minutes. Beyond 12 minutes, the survival rate approaches zero.
Importantly, the more time that passes, the longer the brain is deprived of oxygen and the more likely that brain damage will result. Electrical fibrillation may also be used to treat shockable ventricular tachycardia (xe2x80x9cVTxe2x80x9d). Accordingly, defibrillation is the appropriate therapy for any shockable rhythm, that is, VF or shockable VT.
One way of providing electrical defibrillation uses implantable defibrillators, which are surgically implanted in patients that have a high likelihood of experiencing VF. Implanted defibrillators typically monitor the patient""s heart activity and automatically supply the requisite electrical defibrillation pulses to terminate VF. Implantable defibrillators are expensive, and are used in only a small fraction of the total population at risk for sudden cardiac death.
External defibrillators send electrical pulses to a patient""s heart through electrodes applied to the patient""s torso. External defibrillators are typically located and used in hospital emergency rooms, operating rooms, and emergency medical vehicles. Of the wide variety of external defibrillators currently available, automatic and semi-automatic external defibrillators, collectively referred to as xe2x80x9cAEDsxe2x80x9d, are becoming increasingly popular because relatively inexperienced personnel can use them. U.S. Pat. No. 5,607,454 to Cameron et al., entitled Electrotherapy Method and Apparatus, and PCT publication number WO 94/27674, entitled Defibrillator With Self-Test Features, the entire contents of the specifications of which are hereby incorporated by reference, describe AEDs.
AEDs provide a number of advantages, including the availability of external defibrillation at locations where external defibrillation is not regularly expected, and is likely to be performed quite infrequently, such as in residences, public buildings, businesses, personal vehicles, public transportation vehicles, among other locations. Although operators of AEDs can expect to use an AED only very occasionally, they must nevertheless perform quickly and accurately when called upon. For this reason, AEDs automate many of the steps associated with operating external defibrillation equipment. Along these lines, the operation of AEDs is intended to be simple and intuitive. AEDs typically are designed to minimize the number of operator decisions required.
The present invention provides a method for reducing delay between termination of cardiopulmonary resuscitation and administration of a defibrillating shock. According to the method, an electrocardiogram signal of the patient is monitored during administration of cardiopulmonary resuscitation to a patient. The electrocardiogram signal is analyzed to determine whether a shockable rhythm exists. It is indicated that a shockable rhythm exists and/or that a defibrillating shock will be administered. Cardiopulmonary resuscitation is stopped. The defibrillating shock is administered within 10 seconds of the cessation of cardiopulmonary resuscitation.
Additionally, the present invention provides a defibrillator. The defibrillator includes electrodes for monitoring a patient""s heart rhythm during administration of cardiopulmonary resuscitation and producing an electrocardiogram signal corresponding to the patient""s heart rhythm. A processor operatively connected to the electrodes receives the electrocardiogram signal from the electrodes and analyzes the patient""s heart rhythm to detect a shockable rhythm. An indicator operatively connected to the processor indicates that a shockable rhythm exists and/or that a defibrillating shock is to be administered. Electrodes operatively connected to the power source administer a defibrillating shock to the patient within ten seconds of cessation of cardiopulmonary resuscitation.
Furthermore, the present invention concerns a method for reducing delay between termination of cardiopulmonary resuscitation and administration of a defibrillating shock. According to the method, an electrocardiogram signal of the patient is monitored during administration of cardiopulmonary resuscitation to a patient. The electrocardiogram signal is monitored to determine whether a shockable rhythm exists during administration of cardiopulmonary resuscitation to the patient. A defibrillator is automatically charged during the administering of the cardiopulmonary resuscitation.
Still further, the present invention provides a method for reducing delay between termination of cardiopulmonary resuscitation and administration of a defibrillating shock. The method includes administering the defibrillating shock within 10 seconds of cessation of cardiopulmonary resuscitation.